The environment within homes, offices, and other indoor facilities is often contaminated with a variety of noxious and toxic gases. Such gasses include carbon monoxide, methane, sulfur dioxide, hydrogen sulfide, NO.sub.x, and a broad variety of organic vapors as well. Although these gases may be attributed to outdoor sources, many are prevalent within the indoor environment due to either the captive location of an indoor facility near an outdoor source or to gas emitting activities occurring within the indoor facility itself.
Indoor activities that are known to generate noxious or toxic materials include tobacco smoking, cooking, open fireplaces, faulty appliances, or a variety of other normal activities. These noxious or toxic materials are characterized differently in terms of their effects or impact on the environment. Some may merely have an unpleasant odor; others may accumulate and soil surfaces; while others may be dangerous, actually posing a health hazard to those exposed to the materials. Studies have shown, for example, that exposure to second-hand tobacco smoke significantly increases ones risk of developing lung cancer. Additionally, it has been found that a high proportion of homes contain latent carbon monoxide concentrations responsible for vague disorders such as lassitude and headaches at concentrations far below levels known to produce overt symptoms of toxicity.
Particulate matter is also commonly found in the indoor environment. Tobacco smoking, for example, generates both particles and gasses. Organic aerosols, dust particles, pollen, and minute organisms are further examples of particles typically found floating in the air. Such particles may pose a health hazard due to either the chemical nature of the particle or by the particle's physical size. Environmental standards have been promulgated for particles smaller than about ten micrometers because particles of this size are known to penetrate much deeper into the lungs than coarser particles.
Therefore, because such toxic and noxious materials constitute known health risks and because these materials are prevalent indoors where a majority of time is spent, it is clearly desirable to reduce the concentrations of such noxious and toxic materials in the indoor environment.
Many devices have been marketed over the years in an attempt to assist in this regard. Negative ion generators are regarded by some as effective. However, their effectiveness is largely dependent on particle size, therefore, they are not well suited for the removal of a broad spectrum of gases. Room air fresheners only serve to mask the odors but do nothing to remove the gases or particulate matter from the air. Activated charcoal filters may also be used, however, they are fairly expensive and their effectiveness is dependent on the condition of the charcoal's activated sites. This type of filter losses its effectiveness progressively with use and there is no means to determine the point when the filter becomes ineffective. The result is that either the filter is prematurely discarded or is kept in service long after its useful life.
It is, therefore desirable to provide an air purifier for indoor use for reducing the concentrations of particulates and noxious and toxic gases in the air. It is desirable that this apparatus operate for long periods without being exhausted or require costly replacements. It is desirable that it be effective with respect to a broad spectrum of noxious and toxic materials. It is desirable that it be simple to operate and require low-cost materials. It is also highly desirable that it be attractive since it becomes a permanent fixture in the indoor environment.